Geneva movement for motion picture projection



Aug. l5, 1939. E. MAY 2,169,567

GENEVA MOVEMENT FOR MOTION PICTURE PROJECTION Filed March l5, 1938 INVENTOR 5L" Il I BY l' all gf,

@M @Wwf Patented Aug. 15, 1939 aititssv l GENEVA MOVEMENT FOR MOTION PROJECTION Erwin May, Wetzlar, Germany, assignor to Ernst Leitz, G. m. b. H., Wetzlar, Germany l Application March 15, 1938, Serial No. 195,982 In Germany March 30, 1937 1 Claim.

The Iobject of this invention is to provide a Geneva movement for motion picture projection comprising a combination of elements whereby to obtain a relatively high rotative speed of the star wheel for shifting the film coupled with a relatively low angular accelerationwhereby to prolong the projection periods without subjecting the lm to excessive or destructive stresses.

'Ihe invention is embodied in a Geneva movement having a star wheel with four slots which are successively engaged by the pin in the pin wheel. The pin is radially movable in the pin wheel whereby to obtain a relatively low acceleration of the star wheel when the iilm is shifted.

The pin wheel itself is eccentrically driven whereby to obtain a relatively high rotative speed of the star wheel for shifting the iii/m whereby to shorten the periods during which the film is shifted and lengthen the'projection periods.

The advantage of such a movement is prolonged projection periods without subjecting the lm to excessive or 'destructive tension. The invention will be more fully explained and understood from the following description read together with the accompanying drawing in which Fig. 1 is a view in elevation of a Geneva movement embodying the invention withparts in section and parts broken away. Fig. 2 is a sectional view on the line 2--2 in Fig. 1, but showing the driving pin about to enter a slot in the star Wheel.

Fig. 3 is an explanatory curve diagram.Y Referring to Figs. 1 and 2 the reference numeral 3 denotes the film transport roller of a projection apparatus, details of which are omitted.l The roller is fast on the star wheel shaft 2 which carries the star Wheel If provided with the usual slots 5 which are engaged successively by the pin 4in the pin wheel 'I fast on the driving shaft I2. 'Ihe pin 4 moves lin cam grooves 8 and 9 in fixed bearings I0 and II, the ends of the' pin extendinga'nto the grooves as seen in Fig. 1. The grooves are-circ111ar except the upper portions thereof which are flattened as indicated at 22. The pin wheel is provided with a fork 6 for moving the pin.

When the shaft I2 is actuated the pin wheel T with the pin 4v will be rotated and when the pin enters a slot 5 in the star Wheel to rotate the latter, the pin will move radially inward in the pin wheel as the pin travels in the flattened portions 22 of the grooves 8 and 9. When the pin 6 passes out of engagement with a, slot 5, the stop portions 23 in the star wheel are engaged by the circular surface `24 of the pin wheel 1 in (Cl. 'M -436) the usual manner to keep the star wheel sta-y tionary while the picture is being projected. The pin wheel 'I is cut out as at 25 to permit the arms of the star wheel to pass'.

The shaft I2 is provided with a crank 20 which IS` carries a pin. I3. The latter is engaged by the groove Il in a crank arm I5 fast on a driving shaft 2|. The latter is eccentrically mounted relative to the shaft I2 by any suitable means, not shown. When the shaft 2l s actuated, the 10 shaft I2 is rotated at a speed which is lowest when the crankpin I3 is in the position shown in Fig. 1 and which is highest when the crankpin.

I3 is in the diametrically opposite position, the pin then being farthest away from the center of 15 the shaft 2| and then ofcourse the speed againm decreases during the second half of the. rotation.

The advantages of a Geneva movement embodying this invention are illustrated in Fig. 3 which is a diagram of curves representing the 20 angular acceleration of the star wheel in three different types of Geneva movements for the sake of comparison. Curve I shows the angular acl celeration in a standard Geneva movement, i. e,

a. movement in which the pin is not capableof 2`5 radial movement and the pin wheel shaft is not actuated eccentrically. Curve II shows the ac'- celeration if a standard Geneva movement is provided with the radially movable pin, and curve III illustrates the angular acceleration with the 30 Geneva movement disclosed herein.

.A comparison vof the three curves and their ordinates show's clearly the advantages of .this

- invention inL that. the acceleration in curve III is no greater than in curve I, hence the acceleration 35 is relatively low and has not been increased over that of a standard movement. On the other hand the rotative speed of the star wheel has been increased about one third over that of the standard movement or in other words the time '40 period within which the film is shifted is sho-rtened by one third. Such decrease in the time required to shift the lmcould not be included in thel operation of a Geneva movement exclusive of the radially movable pin without subjecting 45 the film to destructive stresses. The curves demonstrate that a Geneva movement according to this invention results in lengthened projection periods Without subjecting the lm to abnormal stresses. M 50 I claim: s l

A Geneva movement for motion picture projection comprising two fixed spaced plates having opposed symmetrical cam grooves,` a pin extending between said plates tomove in. said cam 55 grooves, a drive shaft exizending through said plates, a pin wheel mounted on said drive shaft in the space between said plates, means in the.

pin wheel engaging said pin to rotate the samek in the said cam grooves, a. star wheel in cooperative relation-with the said pin and pin wheel, said cam grooves including flattened portions for guiding said pin radially in the pin wheel when A ing the drive shaft at a speed which is acceler 5 ated as the pin is moved towards the star wheel.

ERWIN MAY. 

